Technical Field of the Invention
The embodiments of the invention relate to wireless communications and, more particularly, to linking of devices that utilize Bluetooth™ technology.
Description of Related Art
Bluetooth™ (hereinafter “BT”) wireless technology is a short-range communications system utilized to wirelessly link portable and/or fixed electronic devices, such that cables and wires that would normally connect theses devices are not needed. Presently, there are two forms of BT wireless technology systems. One form of BT is the Basic Rate (BR) system, which is also referred to as classic Bluetooth, since this system has been in existence for some time and currently implemented in wirelessly connecting devices. The second form is a newer implementation of BT, known as Low Energy (LE) BT or Bluetooth Low Energy (BLE). Both systems include device discovery, connection establishment and connection mechanisms.
The Basic Rate system includes optional Enhanced Data Rate (EDR) Alternate Media Access Control (MAC) and Physical (PHY) layer extensions. The Basic Rate system offers synchronous and asynchronous connections with data rates of 721.2 Kbps for Basic Rate, 2.1 Mbps for Enhanced Data Rate and high speed operation up to 24 Mbps with the IEEE 802.11 AMP (Alternate MAC PHY) systems. The BLE system includes features designed to enable products that require lower current consumption, lower complexity and lower cost than classic BT using BR/EDR. The BLE system is intended to consume a fraction of the power required for classic BT and a device powered by a button cell battery may power BLE communications for an extended period from the battery. A number of different applications are envisioned for BLE, including medical monitoring and transmission of the monitored data by a wireless link.
Both classic BT and BLE systems generally operate in the unlicensed 2.4 GHz ISM (Industrial, Scientific, Medical) band, typically utilizing one of the IEEE 802.11 protocols (e.g. 802.11a/b/g/n). Both Bluetooth forms are further described in the Bluetooth Specification, such as Bluetooth Specification Version 4.0, Volumes 0-6, published Jun. 30, 2010, which is incorporated by reference herein.
In the BT 4.0 specification for BLE operation, there are five states that a BLE device may be in, of which one is a standby state. In this specification, the BLE scanning and initiation states are specified as two independent and completely separate activities (states). A BLE device which is compliant to the BT 4.0 specification standard does either scanning or initiation. The scanning state is entered to scan for advertisers on a BLE network, while the initiation state is entered to initiate a connection request. Accordingly, in order to perform both functions of scanning and initiating, a BLE device needs to open a receive window a minimum of two times (one receive window for scanning and one receive window for initiating).
When the receive window is open on a device, the device is in a receiving mode for BLE and the radio frequency (RF) front end of the device, as well as the antenna, may be occupied strictly with the receiving function. This implies that during these two receive periods for scanning and initiating, the device is not available for other activities. Opening two receive windows may consume more power than opening a single receive window. More importantly, when the antenna and/or the RF front end is occupied for such receiving times, the radio portion of the device is not able to do other functions due to the multiplexed timing scheme used in BT. This result may reduce the bandwidth efficiency of the device. The problem may compounded when the device has other wireless communication capabilities that it needs to address, such as classic BT, wireless local area network (WLAN) and/or cellular communication (e.g. long term evolution, commonly known as LTE).
It would be advantageous to combine the operations of scanning and initiating into a single receive window opening for a BLE device. Since there is no prohibition in the BT 4.0 specification to use just one receive window, there is no reason why the BLE device could not send out a connection request (initiation) while the device is scanning for advertisers. If the received advertiser address is one that the device wants to make a connection, the BLE device could always send out a connection request, instead of a scan request. This allows only one receive window to be needed to make a BLE connection, instead of two receive windows, yet remain compliant with the BT 4.0 standard. A number of advantages may be obtained with concurrent scanning and initiation, including saving bandwidth and/or reducing power consumption.